Zoom lens and imaging apparatus

ABSTRACT

A zoom lens includes, in order from the object side: a positive first lens group; a negative second lens group; a positive third lens group; a negative fourth lens group; and a positive fifth lens group. The distance between the first and second lens groups constantly increases, the distance between the second and third lens groups constantly decreases, the distance between the third and fourth lens groups constantly changes, and the distance between the fourth and fifth lens groups constantly increases when changing magnification from the wide angle to the telephoto end. The first lens group includes three lenses. The second lens group includes four lenses. The third lens group includes six lenses and an aperture stop. The fifth lens group includes a single lens component.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119 to JapanesePatent Application No. 2014-243845 filed on Dec. 2, 2014. The aboveapplication is hereby expressly incorporated by reference, in itsentirety, into the present application.

BACKGROUND

The present disclosure is related to a zoom lens which is particularlyfavorably suited for use in digital cameras, interchangeable lensdigital cameras, and cinematic cameras. The present disclosure is alsorelated to an imaging apparatus equipped with the zoom lens.

Zoom lenses having five group configurations for use in digital cameras,interchangeable lens digital cameras, and cinematic cameras are known,as disclosed in Japanese Unexamined Patent Publication Nos. 2003-287681,61(1986)-286813, and 2014-102526.

SUMMARY

Recently, the number of pixels in digital cameras, interchangeable lensdigital cameras, and cinematic cameras is increasing. Therefore, thereis demand for a high performance lens to be compatible with theincreased number of pixels, and to favorably correct variousaberrations, as a zoom lens to be employed in these cameras.

In addition, there is demand for the above zoom lens to have a small Fvalue even at the telephoto end. Particularly in so called standard zoomlenses that have zoom ranges that include a focal length of 50 mm as a135 film converted value, there is high demand for a zoom lens having asmall F value even at the telephoto end, from the viewpoint ofexpressivity in photography.

However, the zoom lenses of Japanese Unexamined Patent Publication Nos.2003-287681, 61(1986)-286813, and 2014-102526 have large F values at thetelephoto end, and it also cannot be said that the performance thereofwith respect to correcting aberrations is sufficiently high.Accordingly, there is demand for a zoom lens having a small F valuethroughout the entire zoom range, which favorably corrects variousaberrations.

The present disclosure has been developed in view of the foregoingcircumstances. The present disclosure provides a zoom lens having asmall F value throughout the entire zoom range, which favorably correctsvarious aberrations. The present disclosure also provides an imagingapparatus equipped with such a zoom lens.

A zoom lens of the present disclosure consists of, in order from theobject side to the image side:

a first lens group having a positive refractive power;

a second lens group having a negative refractive power;

a third lens group having a positive refractive power;

a fourth lens group having a negative refractive power; and

a fifth lens group having a positive refractive power;

the distance between the first lens group and the second lens groupconstantly increasing, the distance between the second lens group andthe third lens group constantly decreasing, the distance between thethird lens group and the fourth lens group constantly changing, and thedistance between the fourth lens group and the fifth lens groupconstantly increasing when changing magnification from the wide angleend to the telephoto end;

the first lens group consisting of, in order from the object side to theimage side, a 1-1 negative lens, a 1-2 positive lens, and a 1-3 positivelens;

the second lens group consisting of, in order from the object side tothe image side, a 2-1 negative meniscus lens having a concave surfacetoward the image side, a 2-2 negative lens, a 2-3 positive lens, and a2-4 negative lens;

the third lens group consisting of four positive lenses, two negativelenses, and an aperture stop; and

the fifth lens group consisting of a single lens component.

Here, the expression “lens component” refers to a lens having only asurface toward the object side and a surface toward the image side astwo surfaces that contact air along the optical axis. The expression“single lens component” refers to a one single lens or one set of lensesthat form a cemented lens.

In the zoom lens of the present disclosure, it is preferable forConditional Formula (1) below to be satisfied. Note that it is morepreferable for Conditional Formula (1-1) below to be satisfied.−0.9<(L11f−L12r)/(L11f+L12r)<−0.1  (1)−0.5<(L11f−L12r)/(L11f+L12r)<−0.12  (1−1)

wherein L11f is the paraxial radius of curvature of the surface of the1-1 negative lens toward the object side, and L12r is the paraxialradius of curvature of the surface of the 1-2 positive lens toward theimage side.

In addition, it is preferable for the third lens group to consist of, inorder from the object side to the image side, a 3-1 positive lens, anaperture stop, a 3-2 cemented lens having a positive combined refractivepower, a 3-3 cemented lens having a negative combined refractive power,and a 3-4 positive lens.

In addition, it is preferable for the 3-2 cemented lens to be formed bycementing a negative lens and a biconvex lens, provided in this orderfrom the object side to the image side, together.

In addition, it is preferable for the 3-3 cemented lens to be formed bycementing a positive lens having a convex surface toward the image sideand a biconcave lens, provided in this order from the object side to theimage side, together.

In addition, it is preferable for Conditional Formula (2) below to besatisfied. Note that it is more preferable for Conditional Formula (2-1)below to be satisfied.0.2<f2/L22f<1  (2)0.3<f2/L22f<0.7  (2-1)

wherein f2 is the paraxial focal length of the second lens group withrespect to the d line, and L22f is the paraxial radius of curvature ofthe surface of the 2-2 negative lens toward the object side.

In addition, it is preferable for Conditional Formula (3) below to besatisfied. Note that it is more preferable for Conditional Formula (3-1)below to be satisfied.0.6<f2/f21<1.3  (3)0.7<f2/f21<1.1  (3-1)

wherein f2 is the paraxial focal length of the second lens group withrespect to the d line, and f21 is the paraxial focal length of the 2-1negative lens with respect to the d line.

In addition, it is preferable for Conditional Formula (4) below to besatisfied in the case that the third lens group is constituted by the3-1 positive lens, the aperture stop, the 3-2 cemented lens, the 3-3cemented lens, and the 3-4 positive lens as described above. Note thatit is more preferable for Conditional Formula (4-1) below to besatisfied.0.7<f3/f34<1.6  (4)0.9<f3/f34<1.5  (4-1)

wherein f3 is the paraxial focal length of the third lens group withrespect to the d line, and f34 is the paraxial focal length of the 3-4positive lens with respect to the d line.

In addition, it is preferable for Conditional Formula (5) below to besatisfied. Note that it is more preferable for Conditional Formula (5-1)below to be satisfied.0.2<f3/f31<0.8  (5)0.3<f3/f31<0.7  (5-1)

wherein f3 is the paraxial focal length of the third lens group withrespect to the d line, and f31 is the paraxial focal length of the 3-1positive lens with respect to the d line.

In addition, it is preferable for the fifth lens group to be fixed withrespect to an imaging surface when changing magnification.

In addition, it is preferable for the fifth lens group to consist of asingle lens, and for Conditional Formula (6) below to be satisfied. Notethat it is more preferable for Conditional Formula (6-1) below to besatisfied.15<νd5<40  (6)16<νd5<38  (6-1)

wherein νd5 is the Abbe's number of the single lens with respect to thed line.

In addition, it is preferable for Conditional Formula (7) below to besatisfied. Note that it is more preferable for Conditional Formula (7-1)below to be satisfied.20<νd31<40  (7)25<νd31<35  (7-1)

wherein νd31 is the Abbe's number of the 3-1 positive lens with respectto the d line.

In addition, it is preferable for the fourth lens group to consist of,in order from the object side to the image side, a 4-1 negative lens, a4-2 negative lens, and a 4-3 positive lens; and for the fourth lensgroup to move toward the image side when changing focus from an objectat a far distance to an object at a close distance.

An imaging apparatus of the present disclosure is equipped with the zoomlens of the present disclosure.

Note that the expression “consists of” means that the zoom lens of thepresent disclosure may also include lenses that practically have nopower, optical elements other than lenses such as an aperture stop, amask, a cover glass, and filters, and mechanical components such as lensflanges, a lens barrel, an imaging element, a camera shake correctingmechanism, etc., in addition to the constituent elements listed above.

In addition, the surface shapes of lenses as well as the signs of therefractive powers of lenses are those which are considered in theparaxial region for lenses that include aspherical surfaces.

The zoom lens of the present disclosure consists of, in order from theobject side to the image side: the first lens group having a positiverefractive power; the second lens group having a negative refractivepower; the third lens group having a positive refractive power; thefourth lens group having a negative refractive power; and the fifth lensgroup having a positive refractive power. The distance between the firstlens group and the second lens group constantly increases, the distancebetween the second lens group and the third lens group constantlydecreases, the distance between the third lens group and the fourth lensgroup constantly changes, and the distance between the fourth lens groupand the fifth lens group constantly increases when changingmagnification from the wide angle end to the telephoto end. The firstlens group consists of, in order from the object side to the image side,the 1-1 negative lens, the 1-2 positive lens, and the 1-3 positive lens.The second lens group consists of, in order from the object side to theimage side, a 2-1 negative meniscus lens having a concave surface towardthe image side, a 2-2 negative lens, a 2-3 positive lens, and a 2-4negative lens. The third lens group consists of four positive lenses,two negative lenses, and an aperture stop. The fifth lens group consistsof a single lens component. Therefore, it is possible for the zoom lensto be that which has a small F value throughout the entire zoom rangeand favorably corrects various aberrations.

The imaging apparatus of the present disclosure is equipped with thezoom lens of the present disclosure. Therefore, the imaging apparatuscan obtain images which are bright and have high image quality.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a collection of sectional diagrams that illustrate a firstexample of the configuration of a zoom lens according to an embodimentof the present disclosure (which is common with Example 1).

FIG. 2 is a collection of sectional diagrams that illustrate theconfiguration of a zoom lens according to Example 2.

FIG. 3 is a collection of sectional diagrams that illustrate theconfiguration of a zoom lens according to Example 3.

FIG. 4 is a diagram that illustrates the trajectories of movement whenchanging magnification in a zoom lens according to an embodiment of thepresent disclosure.

FIG. 5 is a collection of diagrams that illustrate aberrations of thezoom lens of Example 1.

FIG. 6 is a collection of diagrams that illustrate aberrations of thezoom lens of Example 2.

FIG. 7 is a collection of diagrams that illustrate aberrations of thezoom lens of Example 3.

FIG. 8 is a perspective view that illustrates the front side of animaging apparatus as an embodiment of the present disclosure.

FIG. 9 is a perspective view that illustrates the rear side of theimaging apparatus illustrated in FIG. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present disclosure will be described indetail with reference to the attached drawings. FIG. 1 is a collectionof sectional diagrams that illustrate the configuration of a zoom lensaccording to an embodiment of the present disclosure, and FIG. 4 is adiagram that illustrates the trajectories of movement when changingmagnification in this zoom lens. The example of the configurationillustrated in FIG. 1 is the same as the configuration of a zoom lens ofExample 1 to be described later. In addition, the movement trajectoriesillustrated in FIG. 4 are common to those of the configurations of zoomlenses of Examples 1 through 3 to be described later. In FIG. 1, theleft side is the object side and the right side is the image side. Theaperture stop St illustrated in FIG. 1 does not necessarily representthe size or shape thereof, but the position of the aperture stop Stalong an optical axis Z. In addition, FIG. 1 illustrates an axial lightbeam wa and a light beam wb at a maximum angle of view.

As illustrated in FIG. 1, this zoom lens is constituted by, in orderfrom the object side to the image side, a first lens group G1 having apositive refractive power, a second lens group G2 having a negativerefractive power, a third lens group G3 having a positive refractivepower, a fourth lens group G4 having a negative refractive power, and afifth lens group G5 having a positive refractive power.

When this zoom lens is applied to an imaging apparatus, it is preferablefor a cover glass, a prism, and various filters, such as an infraredcutoff filter and a low pass filter, to be provided between the opticalsystem and an imaging surface Sim, depending on the configuration of thecamera to which the lens is mounted. Therefore, FIG. 1 and FIG. 2illustrate an example in which a plane parallel plate shaped opticalmember PP that presumes such filters is provided between the lens systemand the imaging surface Sim.

This zoom lens is configured such that the distance between the firstlens group G1 and the second lens group G2 constantly increases, thedistance between the second lens group G2 and the third lens group G3constantly decreases, the distance between the third lens group G3 andthe fourth lens group G4 constantly changes, and the distance betweenthe fourth lens group G4 and the fifth lens group G5 group constantlyincreases when changing magnification from the wide angle end to thetelephoto end. Note that all of the lens groups from the first lensgroup G1 through the fifth lens group G5 may move, or only a portion ofthe lens groups may move, when changing magnification.

Adopting such a configuration is advantageous from the viewpoint ofshortening the total length of the lens system. The advantageous effectof shortening the total length of the lens system becomes particularlyprominent in the case that the zoom lens is applied to a non reflex (socalled mirrorless) type camera, in which back focus is short.

The first lens group G1 has a positive refractive power, and isconstituted by, in order from the object side to the image side, a 1-1negative lens L11, a 1-2 positive lens L12, and a 1-3 positive lens L13.Configuring the first lens group G1 to have a positive refractive poweris advantageous from the viewpoint of shortening the total length of thelens system. In addition, the 1-1 negative lens L11 bears the functionof correcting longitudinal chromatic aberration, lateral chromaticaberration, and spherical aberration. In addition, providing the twopositive lenses, which are the 1-2 positive lens L12 and the 1-3positive lens L13, is advantageous from the viewpoints of suppressingthe generation of spherical aberration while securing the refractivepower of the first lens group G1, shortening the total length of thelens system, and achieving a small F value.

The second lens group G2 has a negative refractive power, and isconstituted by, in order form the object side to the image side, a 2-1negative meniscus lens L21 having a concave surface toward the imageside, a 2-2 negative lens L22, a 2-3 positive lens L23, and a 2-4positive lens L24. The second lens group G2 principally bears thefunction of changing magnification. The 2-1 negative meniscus lens L21suppresses the generation of distortion at the wide angle end, and alsosecures the principal negative refractive power of the second lens groupG2. In addition, by providing a negative lens at the front of the secondlens group G2, the angles of off axis principal light rays that enterthe lenses thereafter with respect to the optical axis can be decreased,which is advantageous from the viewpoint of widening the angle of view.In addition, the 2-2 negative lens L22 shares the burden of bearingnegative refractive power with the 2-1 negative meniscus lens L21, tosuppress the generation of various aberrations. The 2-3 positive lensL23 and the 2-4 positive lens L24 suppress fluctuations in longitudinalchromatic aberration, lateral chromatic aberration, and sphericalaberration caused by changing magnification. In addition, the 2-4negative lens L24 shares the burden of bearing negative refractive powerwith the 2-1 negative meniscus lens L21 and the 2-2 negative lens L22.The heights of off axis principal light rays that pass through the 2-4negative lens L24 are lower compared to those that pass through the 2-1negative meniscus lens L21 at the wide angle end, and the heights ofmarginal axial light rays that pass through the 2-4 negative lens L24are higher compared to those that pass through the 2-1 negative meniscuslens L21 at the telephoto end. Therefore, balance can be achievedbetween longitudinal chromatic aberration and lateral chromaticaberration at the wide angle end and at the telephoto end.

The third lens group G3 has a positive refractive power and isconstituted by four positive lenses, two negative lenses, and anaperture stop. The third lens group G3 principally bears the positiverefracting function of the entire lens system. Spherical aberration canbe favorably maintained while the thickness of the third lens group G3in the direction of the optical axis can be suppressed by providing sixlenses in the third lens group G3. Such a configuration is advantageousfrom the viewpoint of widening the angle of view. In addition, thegeneration of spherical aberration can be suppressed by distributingpositive refractive power among four lenses, particularly at thetelephoto end. This configuration is advantageous from the viewpoint ofachieving a small F value. The generation of higher order sphericalaberration associated with small F values can be suppressed bydistributing negative refractive power between two lenses. In addition,the heights of light rays at peripheral angles of view will become lowby providing the aperture stop St within the third lens group G3. As aresult, imparting the third lens group G3 with a positive refractivepower is facilitated.

Fluctuations in astigmatism in an intermediate region caused by changingmagnification can be corrected, by the fourth lens group G4 having anegative refractive power.

The fifth lens group G5 has a positive refractive power, and isconstituted by a single lens component. The incident angles of lightrays at peripheral angles of view with respect to the imaging surfacecan be decreased, by configuring the fifth lens group G5 to have apositive refractive power. If the number of lenses in the fifth lensgroup G5 increases and the thickness thereof becomes greater, it will benecessary to increase the refractive powers of the second lens group G2and the fourth lens group G4 in order to maintain back focus, resultingin an increase in fluctuations of spherical aberration. Such a problemcan be resolved by configuring the fifth lens group G5 to be constitutedby a single lens component. Note that from this viewpoint, it ispreferable for the fifth lens group G5 to be constituted only by asingle lens.

In addition, it is preferable for Conditional Formula (1) below to besatisfied. The generation of spherical aberration can be suppressed, byconfiguring the zoom lens such that the value of (L11f−L12r)/(L11f+L12r)is not less than or equal to the lower limit defined in ConditionalFormula (1). The generation of astigmatism at the telephoto end can besuppressed, by configuring the zoom lens such that the value of(L11f−L12r)/(L11f+L12r) is not greater than or equal to the upper limitdefined in Conditional Formula (1). Note that more favorably propertiescan be obtained, if Conditional Formula (1-1) below is satisfied.−0.9<(L11f−L12r)/(L11f+L12r)<−0.1  (1)−0.5<(L11f−L12r)/(L11f+L12r)<−0.12  (1-1)

wherein L11f is the paraxial radius of curvature of the surface of the1-1 negative lens toward the object side, and L12r is the paraxialradius of curvature of the surface of the 1-2 positive lens toward theimage side.

In addition, it is preferable for the third lens group G3 to beconstituted by, in order from the object side to the image side, a 3-1positive lens L31, the aperture stop, a 3-2 cemented lens L32 having apositive combined refractive power, a 3-3 cemented lens L33 having anegative combined refractive power, and a 3-4 positive lens L34. By the3-1 positive lens L31 receiving divergent light beams from the secondlens group G2, the diameters of the lenses following thereafter can beprevented from becoming great, and the generation of sphericalaberration can be suppressed. Such a configuration is advantageous fromthe viewpoint of achieving a small F value. In addition, obtaining abalance of lateral chromatic aberration is facilitated, by providinglens components having positive refractive powers with the aperture stopSt interposed therebetween within the third lens group G3. In addition,various aberrations can be favorably corrected, by adopting a positivenegative positive triplet arrangement. In addition, obtaining balance oflongitudinal chromatic aberration, lateral chromatic aberration, andspherical aberration is facilitated, by providing two cemented lenses,which are the 3-2 cemented lens L32 and the 3-3 cemented lens L33.

In addition, it is preferable for the 3-2 cemented lens L32 to be formedby cementing a negative lens L32A and a biconvex lens L32B, provided inthis order from the object side to the image side, together. Thegeneration of differences in spherical aberration depending onwavelengths will be unlikely to occur, particularly at the telephotoend, by adopting such a configuration.

In addition, it is preferable for the 3-3 cemented lens L33 to be formedby cementing a positive lens L33A having a convex surface toward theimage side and a biconcave lens L33B, provided in this order from theobject side to the image side, together. The 3-3 cemented lens L33 isfurther from the aperture stop St than the 3-2 cemented lens L32, andthere are differences in the heights of off axis principal light rays atthe wide angle end and at the telephoto end. Therefore, obtaining abalance of lateral chromatic aberration is facilitated.

In addition, the generation of spherical aberration within the thirdlens group G3 can be suppressed, by forming at least one surface of the3-1 positive lens L31 to be an aspherical surface.

In addition, the generation of astigmatism and spherical aberrationwithin the third lens group G3 can be suppressed, by forming at leastone surface of the 3-4 positive lens L34 to be an aspherical surface.

In addition, it is preferable for Conditional Formula (2) below to besatisfied. The generation of differences in spherical aberrationdepending on wavelengths can be suppressed, particularly at thetelephoto end while distributing negative refractive power between the2-1 negative lens L21 and the 2-2 negative lens L22, by configuring thezoom lens such that the value of f2/L22 is not less than or equal to thelower limit defined in Conditional Formula (2). In addition, thegeneration of negative distortion at the wide angle end can besuppressed, by configuring the zoom lens such that the value of f2/L22is not greater than or equal to the upper limit defined in ConditionalFormula (2). Note that more favorable properties can be obtained ifConditional Formula (2-1) below is satisfied.0.2<f2/L22f<1  (2)0.3<f2/L22f<0.7  (2-1)

wherein f2 is the paraxial focal length of the second lens group withrespect to the d line, and L22f is the paraxial radius of curvature ofthe surface of the 2-2 negative lens toward the object side.

In addition, it is preferable for Conditional Formula (3) below to besatisfied. Configuring the zoom lens such that the value of f2/f21 isnot less than or equal to the lower limit defined in Conditional Formula(3) is advantageous from the viewpoint of widening the angle of view.Fluctuations in spherical aberrations caused by changing magnificationcan be suppressed, by configuring the zoom lens such that the value off2/f21 is not greater than or equal to the upper limit defined inConditional Formula (3). Note that more favorable properties can beobtained if Conditional Formula (3-1) below is satisfied.0.6<f2/f21<1.3  (3)0.7<f2/f21<1.1  (3-1)

wherein f2 is the paraxial focal length of the second lens group withrespect to the d line, and f21 is the paraxial focal length of the 2-1negative lens with respect to the d line.

In addition, it is preferable for Conditional Formula (4) below to besatisfied. The rearward principal point of the third lens group G3 canmoved toward the image side, by configuring the zoom lens such that thevalue of f3/f34 is not less than or equal to the lower limit defined inConditional Formula (4). As a result, securing back focus isfacilitated. In addition, the generation of spherical aberration can besuppressed, by configuring the zoom lens such that the value of f3/f34is not greater than or equal to the upper limit defined in ConditionalFormula (4). Note that more favorable properties can be obtained ifConditional Formula (4-1) below is satisfied.0.7<f3/f34<1.6  (4)0.9<f3/f34<1.5  (4-1)

wherein f3 is the paraxial focal length of the third lens group withrespect to the d line, and f34 is the paraxial focal length of the 3-4positive lens with respect to the d line.

In addition, it is preferable for Conditional Formula (5) below to besatisfied. Obtaining a balance of lateral chromatic aberration isfacilitated, by configuring the zoom lens such that the value of f3/f31is not less than or equal to the lower limit defined in ConditionalFormula (5). In addition, the generation of spherical aberration can besuppressed, by configuring the zoom lens such that the value of f3/f31is not greater than or equal to the upper limit defined in ConditionalFormula (5). In addition, the rearward principal point of the third lensgroup G3 can be prevented from being excessively toward the object side.As a result, maintaining back focus is facilitated. Note that morefavorable properties can be obtained if Conditional Formula (5-1) belowis satisfied.0.2<f3/f31<0.8  (5)0.3<f3/f31<0.7  (5-1)

wherein f3 is the paraxial focal length of the third lens group withrespect to the d line, and f31 is the paraxial focal length of the 3-1positive lens with respect to the d line.

In addition, it is preferable for the fifth lens group G5 to be fixedwith respect to the imaging surface Sim when changing magnification. Thelenses and a lens barrel can be sealed by adopting this configuration,and the entry of foreign can be prevented thereby. Foreign matter islikely to be pictured particularly in non reflex type cameras.Therefore, such a configuration is effective in preventing foreignmatter from being pictured in the case that the zoom lens is applied tosuch cameras.

In addition, it is preferable for the fifth lens group G5 to beconstituted by a single lens, and for Conditional Formula (6) below tobe satisfied. Securing of back focus is facilitated by configuring thefifth lens group G5 such that it consists of a single lens. In addition,fluctuations in lateral chromatic aberration between the wide angle endand the telephoto end can be suppressed, by Conditional Formula (6)being satisfied. Note that more favorable properties can be obtained ifConditional Formula (6-1) below is satisfied.15<νd5<40  (6)16<νd5<38  (6-1)

wherein νd5 is the Abbe's number of the single lens with respect to thed line.

In addition, it is preferable for camera shake prevention to beperformed by moving the 3-3 cemented lens L33 of the third lens group G3in a direction perpendicular to the optical axis. The 3-3 cemented lensL33 is comparatively close to the aperture stop St, and therefore theheights of off axis light beams are low, and it is easy to suppressfluctuations in astigmatism due to shake preventing operations. Inaddition, imparting a strong negative refractive power to the 3-3cemented lens L33 is facilitated by the being interposed between the 3-2cemented lens L32 having a positive refractive power and the 3-4positive lens L34. Such a configuration is advantageous from theviewpoint of decreasing the amount of movement during shake preventingoperations.

In addition, it is preferable for Conditional Formula (7) below to besatisfied. Fluctuations in lateral chromatic aberration at the wideangle end and at the telephoto end can be suppressed by ConditionalFormula (7) being satisfied. Note that more favorable properties can beobtained if Conditional Formula (7-1) below is satisfied.20<νd31<40  (7)25<νd31<35  (7-1)

wherein νd31 is the Abbe's number of the 3-1 positive lens with respectto the d line.

In addition, it is preferable for the fourth lens group G4 to beconstituted by, in order from the object side to the image side, a 4-1negative lens L41, a 4-2 negative lens L42, and a 4-3 positive lens L43,and to be configured to move toward the image side when changing focusfrom an object at a far distance to an object at a close distance. Byproviding two negative lenses toward the object side, the forwardprincipal point of the fourth lens group G4 can be moved toward theobject side, and focusing sensitivity can be increased withoutincreasing the negative refractive power of the fourth lens group G4 asa whole. As a result, the amount of movement of the fourth lens group G4during focusing operations can be decreased. In addition, negativerefractive power can be distributed by providing two negative lenses.Therefore, fluctuations in spherical aberration and astigmatism duringfocusing operations can be suppressed. Note that fluctuations inspherical aberration and astigmatism during focusing operations can besuppressed more effectively, by the 4-1 negative lens L41 and the 4-2negative lens L42 both having a surface toward the image side with aradius of curvature of a lower absolute value than that of the surfacetoward the object side.

In the case that the present zoom lens is to be utilized in anenvironment in which the zoom lens is likely to be damaged, it ispreferable for a protective multiple layer film coating to beadministered. Further, a reflection preventing coating may beadministered in order to reduce the amount of ghost light during use, inaddition to the protective coating.

In addition, FIG. 1 illustrates an example in which the optical memberPP is provided between the lens system and the imaging surface Sim.Alternatively, various filters such as low pass filters and filters thatcut off specific wavelength bands may be provided among each of thelenses instead of being provided between the lens system and the imagingsurface Sim. As a further alternative, coatings that have the samefunctions as the various filters may be administered on the surfaces ofthe lenses.

Next, examples of numerical values of the zoom lens of the presentdisclosure will be described.

First, the zoom lens of Example 1 will be described. FIG. 1 is acollection of sectional diagrams that illustrate the lens configurationof the zoom lens of Example 1. Note that in FIG. 1 and FIGS. 2 and 3that correspond to Examples 2 and 3 to be described later, the left sideis the object side, the right side is the image side, and the aperturestops St in the drawings do not necessarily represent the size or theshape thereof, but the position thereof along the optical axis Z. Notethat the aperture stops St of Examples 1 through 3 are variable stops.

Basic lens data are shown in Table 1, data related to various items areshown in Table 2, data related to the distances among movable surfacesare shown in Table 3, and aspherical surface coefficients are shown inTable 4, for the zoom lens of Example 1. In the following description,the meanings of the symbols in the tables will be described forExample 1. The meanings of the symbols are basically the same forExamples 2 and 3.

In the lens data of Table 1, surface numbers that sequentially increasefrom the object side to the image side, with the surface of theconstituent element at the most object side designated as first, areshown in the column “Surface Number”. The radii of curvature of ithsurfaces are shown in the column of “Radius of Curvature”, the distancesalong the optical axis Z between each surface and a next surface areshown in the column “Distance”. The refractive indices of each opticalelement with respect to the d line (wavelength: 587.6 nm) are shown inthe column nd. The Abbe's numbers of each optical element with respectto the d line (wavelength: 587.6 nm) are shown in the column νd.

Here, the signs of the radii of curvature are positive in cases that thesurface shape is convex toward the object side, and negative in casesthat the surface shape is convex toward the image side. The aperturestop St and the optical member PP are also included in the basic lensdata. Text reading “(aperture stop)” is indicated along with a surfacenumber in the column of the surface numbers at the surface correspondingto the aperture stop. In addition, DD [surface number] is indicated inthe column “Distance” for distances that change while changingmagnification. The numerical values corresponding to DD [surface number]are shown in Table 3.

Table 2 shows the values of the zoom magnification rates of the entiresystem, the focal lengths “f′”, the back focus “Bf′”, F values “F No.”,the angles of view “2ω”, at the wide angle end, at an intermediateposition, and at the telephoto end, respectively, as the data related tovarious items.

In the basic lens data, the data related to various items, and the datarelated to the movable surfaces, degrees are used as the units forangles and mm are used as the units for lengths. However, it is possiblefor optical systems to be proportionately enlarged or proportionatelyreduced and utilized. Therefore, other appropriate units may be used.

In the lens data of Table 1, the symbol “*” is appended to the surfacenumbers of aspherical surfaces, and numerical values that represent theparaxial radii of curvature are shown as the radii of curvature of theaspherical surfaces. The data of Table 4 related to aspherical surfacecoefficients show the surface numbers of the aspherical surfaces andaspherical surface coefficients related to the aspherical surfaces. Theaspherical coefficients are the values of coefficients KA and Am(m=3˜16) in the aspherical surface formula below.Zd=C·h ²/{1+(1−KA·C ² ·h ²)^(1/2) }+ΣAm·h ^(m)

wherein: Zd is the depth of the aspherical surface (the length of anormal line from a point on the aspherical surface at a height h to aplane perpendicular to the optical axis in contact with the peak of theaspherical surface), h is height (the distance from the optical axis), Cis the inverse of the paraxial radius of curvature, and KA and Am(m=3˜16) are aspherical surface coefficients.

TABLE 1 Example 1: Lens Data Surface Number Radius of Curvature Distancend νd 1 86.20982 2.210 1.84666 23.78 2 54.35200 6.000 1.61800 63.33 3139.31177 0.100 4 53.19269 6.340 1.75500 52.32 5 200.56627 DD [5]  *6141.91654 1.400 1.85135 40.10 *7 13.47772 8.570 8 −32.15762 1.0101.69680 55.53 9 17.98900 7.500 1.90366 31.31 10 −39.71555 1.380 11−21.64392 1.000 1.72916 54.68 12 −56.68875 DD [12] *13 27.66531 4.0001.68458 30.88 *14 −787.32682 2.000 15 (aperture ∞ 3.440 stop) 1635.85993 1.010 1.84666 23.78 17 15.92500 6.280 1.53775 74.70 18−48.19335 0.500 19 396.51587 3.510 1.49700 81.54 20 −39.57800 0.8001.79952 42.22 21 31.95551 1.810 *22 20.62352 5.760 1.61882 63.58 *23−26.89463 DD [23] 24 ∞ 0.800 1.61800 63.33 25 22.13057 2.050 26 ∞ 0.8101.84666 23.78 27 45.98400 2.540 1.49700 81.54 28 −121.37904 DD [28] 29310.67587 3.000 1.95906 17.47 30 −80.18906 19.630  31 ∞ 2.150 1.5476354.98 32 ∞ 0.700 1.49784 54.98 33 ∞ 0.513

TABLE 2 Example 1: Items (d line) Wide Angle End Intermediate TelephotoEnd Zoom Ratio 1.0 1.9 3.2 f′ 16.492 31.059 53.436 Bf′ 22.000 22.00022.000 F No. 2.88 2.74 2.89 2ω (°) 87.0 48.6 28.8

TABLE 3 Example 1: Zoom Distances Wide Angle End Intermediate TelephotoEnd DD [5] 0.800 12.276 26.783 DD [12] 19.890 5.636 0.685 DD [23] 2.0006.395 7.257 DD [28] 2.600 7.250 14.396

TABLE 4 Example 1: Aspherical Surface Coefficients Surface Number 6 7 13KA 1.0000000E+00 −1.3833082E+00   1.0000000E+00 A3 0.0000000E+000.0000000E+00  0.0000000E+00 A4 −2.6826923E−05  5.1722084E−05 4.1332336E−06 A5 4.7863658E−06 1.9249650E−05 −8.6972277E−06 A6−1.8421337E−07  −4.6557231E−06   1.5350565E−06 A7 −1.8337031E−08 6.8086230E−07 −7.8404429E−08 A8 1.6991972E−09 −4.6108053E−08 −7.4982002E−09 A9 4.0861337E−11 −1.7600435E−09   8.8156832E−10 A10−7.8511430E−12  4.5574120E−10 −9.4816394E−12 A11 −4.3078650E−14 −5.9515764E−12  −6.2840110E−13 A12 2.3184894E−14 −1.9499420E−12 −2.4248166E−14 A13 4.1106169E−17 1.9031053E−14 A14 −4.8125491E−17 5.4999737E−15 A15 3.8585298E−19 1.9283343E−16 A16 2.7390609E−20−2.0233351E−17  Surface Number 14 22 23 KA 1.0000000E+00 1.0000000E+001.0000000E+00 A3 0.0000000E+00 0.0000000E+00 0.0000000E+00 A41.0143172E−05 −4.8240511E−05  −4.3314253E−07  A5 −6.3304378E−06 5.2748685E−06 1.6554907E−06 A6 8.2811414E−07 −6.2154451E−07 5.7603232E−07 A7 1.0571100E−08 −4.8032329E−08  −2.3889843E−07  A8−6.8812553E−09  1.3275405E−08 2.0442912E−08 A9 −2.0359431E−10 6.1331416E−10 2.1682367E−09 A10 6.3325383E−11 −2.2421975E−10 −3.8023797E−10  A11 −3.4680139E−14  −3.4333485E−12  −5.6322606E−12  A12−1.5600198E−13  2.2269472E−12 2.8361883E−12 A13 2.2654836E−149.7304729E−15 A14 −1.4106854E−14  −1.0948330E−14  A15 −1.1949080E−16 −5.6980089E−16  A16 4.6802864E−17 6.3788931E−17

FIG. 5 is a collection of diagrams that illustrate various aberrationsof the zoom lens of Example 1. The spherical aberration, theastigmatism, the distortion, and the lateral chromatic aberration of thezoom lens of Example 1 at the wide angle end are illustrated in thisorder from the left side of the drawing sheet at the upper portion ofFIG. 5. The spherical aberration, the astigmatism, the distortion, andthe lateral chromatic aberration of the zoom lens of Example 1 at anintermediate focal distance are illustrated are illustrated in thisorder from the left side of the drawing sheet at the middle portion ofFIG. 5. The spherical aberration, the astigmatism, the distortion, andthe lateral chromatic aberration of the zoom lens of Example 1 at thetelephoto end are illustrated in are illustrated in this order from theleft side of the drawing sheet at the lower portion of FIG. 5. Thediagrams that illustrate spherical aberration, astigmatism, anddistortion show aberrations using the d line (wavelength: 587.6 nm) as areference wavelength. The diagrams that illustrate spherical aberrationshow aberrations related to the d line (wavelength: 587.6 nm),aberrations related to the C line (wavelength: 656.3 nm), aberrationsrelated to the F line (wavelength: 486.1 nm), and aberrations related tothe g line (wavelength: 435.8 nm) as solid lines, long broken lines,short broken lines, and solid gray lines, respectively. In the diagramsthat illustrate astigmatism, aberrations in the sagittal direction andaberrations in the tangential direction are indicated by solid lines andshort broken lines, respectively. In the diagrams that illustratelateral chromatic aberration, aberrations related to the C line(wavelength: 656.3 nm), aberrations related to the F line (wavelength:486.1 nm), and aberrations related to the g line (wavelength: 435.8 nm)are shown as long broken lines, short broken lines, and solid graylines, respectively. Note that these vertical aberrations are all for astate focused on an object at infinity. In the diagrams that illustratespherical aberrations, “FNo.” denotes F values. In the other diagramsthat illustrate the aberrations, “ω” denotes half angles of view.

The symbols, the meanings, and the manner in which the data are shown inthe description of Example 1 above are the same for the followingExamples to be described later, unless particularly noted. Therefore,redundant descriptions thereof will be omitted below.

Next, a zoom lens according to Example 2 will be described. FIG. 2 is acollection of sectional diagrams that illustrate the lens configurationof the zoom lens of Example 2. In addition, basic lens data are shown inTable 5, data related to various items are shown in Table 6, datarelated to the distances among movable surfaces are shown in Table 7,data related to aspherical surface coefficients are shown in Table 8,and various aberrations are illustrated in FIG. 6 for the zoom lens ofExample 2.

TABLE 5 Example 2: Lens Data Surface Number Radius of Curvature Distancend νd 1 69.44254 1.810 1.84661 23.88 2 48.31867 6.000 1.61800 63.33 395.72888 0.100 4 49.20902 6.512 1.75500 52.32 5 154.36104 DD [5]  *6166.66082 2.000 1.85135 40.10 *7 12.87033 8.647 8 −37.26424 1.0101.69680 55.53 9 16.63285 7.779 1.90366 31.31 10 −47.15324 1.412 11−23.28964 1.000 1.72916 54.68 12 −53.90192 DD [12] *13 32.79803 4.0001.68893 31.16 *14 −435.72457 2.000 15 (aperture ∞ 3.250 stop) 1625.23382 1.010 1.92286 18.90 17 17.17597 6.399 1.49700 81.54 18−36.90322 0.500 19 −105.78645 3.510 1.49700 81.54 20 −20.26114 0.8001.79952 42.22 21 27.63093 1.254 *22 18.78974 6.322 1.62087 63.88 *23−21.61987 DD [23] 24 972.23964 0.800 1.61800 63.33 25 21.08780 1.955 26192.68481 0.810 1.80518 25.42 27 45.24288 2.200 1.49700 81.54 28−597.47357 DD [28] 29 −167.22535 3.000 1.95906 17.47 30 −47.0200219.692  31 ∞ 2.150 1.54763 54.98 32 ∞ 0.700 1.49784 54.98 33 ∞ 0.508

TABLE 6 Example 2: Items (d line) Wide Angle End Intermediate TelephotoEnd Zoom Ratio 1.0 1.6 3.2 f′ 16.492 26.825 53.436 Bf′ 22.057 22.05722.057 F No. 2.88 2.88 2.89 2ω[°] 86.8 56.0 29.4

TABLE 7 Example 2: Zoom Distances Wide Angle End Intermediate TelephotoEnd DD [5] 1.000 9.295 26.548 DD [12] 19.982 7.400 0.679 DD [23] 2.0005.760 6.470 DD [28] 2.770 4.961 15.705

TABLE 8 Example 2: Aspherical Surface Coefficients Surface Number 6 7 13KA 1.0000000E+00 −6.5707483E−01   1.0000000E+00 A3 0.0000000E+000.0000000E+00  0.0000000E+00 A4 −2.0790660E−05  3.4578052E−05−1.2805886E−06 A5 5.0301042E−06 1.7338444E−05 −8.4541158E−06 A6−2.2580782E−07  −3.9506743E−06   1.5320931E−06 A7 −2.1147040E−08 6.3384844E−07 −8.3453051E−08 A8 1.8971048E−09 −4.6708214E−08 −6.8558113E−09 A9 4.6926156E−11 −1.6027268E−09   9.0350379E−10 A10−8.0097565E−12  4.5667638E−10 −9.6794672E−12 A11 −5.6797110E−14 −4.3832129E−12  −1.0444535E−12 A12 2.3114290E−14 −2.2424127E−12 −1.2103292E−15 A13 1.8100796E−17 1.9261678E−14 A14 −4.5226749E−17 5.7153805E−15 A15 3.9766943E−19 3.6051947E−16 A16 2.3880803E−20−2.8728456E−17  Surface Number 14 22 23 KA 1.0000000E+00 1.0000000E+001.0000000E+00 A3 0.0000000E+00 0.0000000E+00 0.0000000E+00 A47.9960282E−07 −6.9438028E−05  4.2172253E−07 A5 −6.4319161E−06 5.1694854E−06 2.4603725E−06 A6 8.1815014E−07 −5.3141923E−07 5.6813906E−07 A7 1.8444749E−08 −5.4939173E−08  −2.5134824E−07  A8−7.1598897E−09  1.3456267E−08 2.1034835E−08 A9 −2.1326637E−10 6.2400311E−10 2.2589783E−09 A10 6.2609571E−11 −2.3068662E−10 −3.9432402E−10  A11 3.1119769E−13 −3.6502480E−12  −5.8112435E−12  A12−1.6732195E−13  2.2954541E−12 2.9647347E−12 A13 2.7633652E−149.7998563E−15 A14 −1.4614387E−14  −1.1245406E−14  A15 −1.2326490E−16 −6.0807879E−16  A16 4.5852693E−17 6.4589171E−17

Next, a zoom lens according to Example 3 will be described. FIG. 3 is acollection of sectional diagrams that illustrate the lens configurationof the zoom lens of Example 3. In addition, Basic lens data are shown inTable 9, data related to various items are shown in Table 10, datarelated to the distances among movable surfaces are shown in Table 11,data related to aspherical surface coefficients are shown in Table 12,and various aberrations are illustrated in FIG. 7 for the zoom lens ofExample 3.

TABLE 9 Example 3: Lens Data Surface Number Radius of Curvature Distancend νd 1 76.44802 1.810 1.84661 23.88 2 51.56054 6.024 1.61800 63.33 3119.04201 0.100 4 55.79377 6.072 1.75500 52.32 5 205.02447 DD [5]  *6151.44478 2.000 1.85135 40.10 *7 13.37604 8.454 8 −37.83715 1.0101.69680 55.53 9 17.12431 7.893 1.90366 31.31 10 −41.50609 1.205 11−23.85142 1.000 1.72916 54.68 12 −96.38918 DD [12] *13 30.53747 4.0001.68893 31.16 *14 −577.09433 2.000 15 (aperture ∞ 3.652 stop) 1630.40620 1.010 1.92286 18.90 17 19.31761 6.246 1.49700 81.54 18−33.00050 0.500 19 −422.28074 3.510 1.49700 81.54 20 −23.67547 0.8001.79952 42.22 21 31.29122 1.671 *22 19.74958 5.839 1.62087 63.88 *23−26.27159 DD [23] 24 −736.81576 0.800 1.61800 63.33 25 21.29420 2.235 26−364.08563 0.810 1.80518 25.42 27 48.68916 2.582 1.49700 81.54 28−99.88406 DD [28] 29 220.56869 3.000 1.95906 17.47 30 −79.47003 19.687 31 ∞ 2.150 1.54763 54.98 32 ∞ 0.700 1.49784 54.98 33 ∞ 0.513

TABLE 10 Example 3: Items (d line) Wide Angle End Intermediate TelephotoEnd Zoom Ratio 1.0 1.6 3.2 f′ 16.492 26.825 53.436 Bf′ 22.056 22.05622.056 F No. 2.88 2.88 2.89 2ω[°] 88.2 56.6 29.2

TABLE 11 Example 3: Zoom Distances Wide Angle End Intermediate TelephotoEnd DD [5] 0.800 8.710 27.211 DD [12] 20.165 8.236 0.684 DD [23] 2.0005.679 8.130 DD [28] 2.558 6.070 12.968

TABLE 12 Example 3: Aspherical Surface Coefficients Surface Number 6 713 KA 1.0000000E+00 −1.6074200E+00   1.0000000E+00 A3 0.0000000E+000.0000000E+00  0.0000000E+00 A4 −2.5262922E−05  7.2068095E−05 2.6877347E−06 A5 4.4097795E−06 1.7083360E−05 −8.6383638E−06 A6−1.7700080E−07  −4.3563271E−06   1.5598520E−06 A7 −1.8337577E−08 6.5542961E−07 −8.0520831E−08 A8 1.7477965E−09 −4.6860578E−08 −7.4712923E−09 A9 4.2100081E−11 −1.6453238E−09   8.8374702E−10 A10−7.9771762E−12  4.5875560E−10 −9.2048146E−12 A11 −5.3236937E−14 −5.0240999E−12  −7.1357212E−13 A12 2.2906373E−14 −2.0232118E−12 −1.7781736E−14 A13 4.1770049E−17 1.4469311E−14 A14 −4.4454593E−17 5.0703031E−15 A15 4.2736425E−19 2.6938032E−16 A16 1.9987097E−20−2.1887624E−17  Surface Number 14 22 23 KA 1.0000000E+00 1.0000000E+001.0000000E+00 A3 0.0000000E+00 0.0000000E+00 0.0000000E+00 A48.6544405E−06 −5.7314144E−05  −5.2039171E−06  A5 −6.3419377E−06 5.6268422E−06 2.6858624E−06 A6 8.3378906E−07 −5.9376227E−07 6.0308104E−07 A7 1.1522855E−08 −5.0222306E−08  −2.4897247E−07  A8−6.6849880E−09  1.3105598E−08 2.0248278E−08 A9 −2.2795091E−10 6.0074452E−10 2.2021883E−09 A10 6.2326332E−11 −2.3312863E−10 −3.8663923E−10  A11 7.5748892E−14 −3.5379162E−12  −5.6426991E−12  A12−1.5294111E−13  2.3294931E−12 2.9204281E−12 A13 2.8795069E−141.2247572E−14 A14 −1.4288029E−14  −1.0904473E−14  A15 −1.3394466E−16 −5.9016344E−16  A16 4.0233296E−17 5.7585817E−17

Table 13 shows values corresponding to Conditional Formulae (1) through(7) for the zoom lenses of Examples 1 through 3. Note that all of theExamples use the d line as a reference wavelength, and the values shownin Table 13 are those with respect to the reference wavelength.

TABLE 13 Formula Condition Example 1 Example 2 Example 3 (1) (L11f −L12r)/ −0.235 −0.159 −0.218 (L11f + L12r) (2) f2/L22f 0.457 0.400 0.383(3) f2/f21 0.836 0.905 0.835 (4) f3/f34 1.160 1.334 1.191 (5) f3/f310.586 0.517 0.538 (6) νd5 17.47 17.47 17.47 (7) νd31 30.88 31.16 31.16

Based on the data above, it can be understood that all of the zoomlenses of Examples 1 through 3 satisfy Conditional Formulae (1) through(7), and that these zoom lenses have small F values of 3.0 or less andfurther 2.9 or less throughout the entire zoom range, and favorablycorrect various aberrations. Note that all of the zoom lenses ofExamples 1 through 3 are standard zoom lenses that have zoom ranges thatinclude a focal length of 50 mm as a 135 film converted value. However,the values of the focal lengths f′ shown as items of the Examples arenot 135 film converted focal lengths themselves. The values of the focallengths as 135 film converted focal lengths are approximately 1.5 timesthe values of the focal lengths f′.

Next, an imaging apparatus according to an embodiment of the presentdisclosure will be described with reference to FIG. 8 and FIG. 9. FIG. 8and FIG. 9 respectively are perspective views of the front and the rearof a camera 30. The camera 30 is a non reflex (so called mirrorless),onto which an exchangeable lens 20 is interchangeably mounted. Theexchangeable lens 20 is a zoom lens 1 according to an embodiment of thepresent disclosure housed in a lens barrel.

The camera 30 is equipped with a camera body 31. A shutter releasebutton 32 and a power button 33 are provided on the upper surface of thecamera body 31. Operating sections 34 and 35 and a display section 36are provided on the rear surface of the camera body 31. The displaysection 36 displays images which have been photographed and imageswithin the angle of view prior to photography.

A photography opening, in to which light from targets of photographyenters, is provided at the central portion of the front surface of thecamera body 31. A mount 37 is provided at a position corresponding tothe photography opening. The exchangeable lens 20 is mounted onto thecamera body 31 via the mount 37.

An imaging element (not shown), such as a CCD that receives images ofsubjects formed by the exchangeable lens 20 and outputs image signalscorresponding to the images, a signal processing circuit (not shown)that processes the image signals output by the imaging element togenerate images, and a recording medium (not shown) for recording thegenerated images, are provided within the camera body 31. In this camera30, photography of a still image corresponding to a single frame orvideo imaging is enabled by pressing the shutter release button 32.Image data obtained by photography or video imaging are recorded in therecording medium.

The camera 30 of the present embodiment is equipped with the zoom lens 1of the present disclosure. Therefore, the camera 30 is capable ofobtaining bright images having wide angles of view and high imagequality.

The present disclosure has been described with reference to theembodiments and Examples thereof. However, the zoom lens of the presentdisclosure is not limited to the embodiments and Examples describedabove, and various modifications are possible. For example, the valuesof the radii of curvature of each lens component, the distances amongsurfaces, the refractive indices, the Abbe's numbers, and the asphericalsurface coefficients may be changed as appropriate.

In addition, a non reflex digital camera was described as the embodimentof the imaging apparatus. However, the present disclosure is not limitedto this application, and may be applied to other imaging apparatuses,such as a video camera, digital cameras other than those of the nonreflex type, a cinematic camera, and a broadcast camera.

What is claimed is:
 1. A zoom lens consisting of, in order from theobject side to the image side: a first lens group having a positiverefractive power; a second lens group having a negative refractivepower; a third lens group having a positive refractive power; a fourthlens group having a negative refractive power; and a fifth lens grouphaving a positive refractive power; the distance between the first lensgroup and the second lens group constantly increasing, the distancebetween the second lens group and the third lens group constantlydecreasing, the distance between the third lens group and the fourthlens group constantly changing, and the distance between the fourth lensgroup and the fifth lens group constantly increasing when changingmagnification from the wide angle end to the telephoto end; the firstlens group consisting of, in order from the object side to the imageside, a 1-1 negative lens, a 1-2 positive lens, and a 1-3 positive lens;the second lens group consisting of, in order from the object side tothe image side, a 2-1 negative meniscus lens having a concave surfacetoward the image side, a 2-2 negative lens, a 2-3 positive lens, and a2-4 negative lens; the third lens group consisting of four positivelenses, two negative lenses, and an aperture stop; and the fifth lensgroup consisting of a single lens component, wherein the third lensgroup consists of, in order from the object side to the image side, a3-1 positive lens, an aperture stop, a 3-2 cemented lens having apositive combined refractive power, a 3-3 cemented lens having anegative combined refractive power, and a 3-4 positive lens.
 2. A zoomlens as defined in claim 1, in which Conditional Formula (1) below issatisfied:−0.9<(L11f−L12r)/(L11f+L12r)<−0.1  (1) wherein L1 if is the paraxialradius of curvature of the surface of the 1-1 negative lens toward theobject side, and L12r is the paraxial radius of curvature of the surfaceof the 1-2 positive lens toward the image side.
 3. A zoom lens asdefined in claim 1, wherein: the 3-2 cemented lens is formed bycementing a negative lens and a biconvex lens, provided in this orderfrom the object side to the image side, together.
 4. A zoom lens asdefined in claim 1, wherein: the 3-3 cemented lens is formed bycementing a positive lens having a convex surface toward the image sideand a biconcave lens, provided in this order from the object side to theimage side, together.
 5. A zoom lens as defined in claim 1, in whichConditional Formula (2) below is satisfied:0.2<f2/L22f<1  (2) wherein f2 is the paraxial focal length of the secondlens group with respect to the d line, and L22f is the paraxial radiusof curvature of the surface of the 2-2 negative lens toward the objectside.
 6. A zoom lens as defined in claim 1, in which Conditional Formula(3) below is satisfied:0.6<f2/f21<1.3  (3) wherein f2 is the paraxial focal length of thesecond lens group with respect to the d line, and f21 is the paraxialfocal length of the 2-1 negative lens with respect to the d line.
 7. Azoom lens as defined in claim 1, in which Conditional Formula (4) belowis satisfied:0.7<f3/f34<1.6  (4) wherein f3 is the paraxial focal length of the thirdlens group with respect to the d line, and f34 is the paraxial focallength of the 3-4 positive lens with respect to the d line.
 8. A zoomlens as defined in claim 1, in which Conditional Formula (5) below issatisfied:0.2<f3/f31<0.8  (5) wherein f3 is the paraxial focal length of the thirdlens group with respect to the d line, and f31 is the paraxial focallength of the 3-1 positive lens with respect to the d line.
 9. A zoomlens as defined in claim 1, wherein: the fifth lens group is fixed withrespect to an imaging surface when changing magnification.
 10. A zoomlens as defined in claim 1, wherein: the fifth lens group consists of asingle lens; and Conditional Formula (6) below is satisfied:15<νd5<40  (6) wherein νd5 is the Abbe's number of the single lens withrespect to the d line.
 11. A zoom lens as defined in claim 1, in whichConditional Formula (7) below is satisfied:20<νd31<40  (7) wherein νd31 is the Abbe's number of the 3-1 positivelens with respect to the d line.
 12. A zoom lens consisting of, in orderfrom the object side to the image side: a first lens group having apositive refractive power; a second lens group having a negativerefractive power; a third lens group having a positive refractive power;a fourth lens group having a negative refractive power; and a fifth lensgroup having a positive refractive power; the distance between the firstlens group and the second lens group constantly increasing, the distancebetween the second lens group and the third lens group constantlydecreasing, the distance between the third lens group and the fourthlens group constantly changing, and the distance between the fourth lensgroup and the fifth lens group constantly increasing when changingmagnification from the wide angle end to the telephoto end; the firstlens group consisting of, in order from the object side to the imageside, a 1-1 negative lens, a 1-2 positive lens, and a 1-3 positive lens;the second lens group consisting of, in order from the object side tothe image side, a 2-1 negative meniscus lens having a concave surfacetoward the image side, a 2-2 negative lens, a 2-3 positive lens, and a2-4 negative lens; the third lens group consisting of four positivelenses, two negative lenses, and an aperture stop; and the fifth lensgroup consisting of a single lens component, wherein: the fourth lensgroup consists of, in order from the object side to the image side, a4-1 negative lens, a 4-2 negative lens, and a 4-3 positive lens; and thefourth lens group moves toward the image side when changing focus froman object at a far distance to an object at a close distance.
 13. A zoomlens as defined in claim 1, in which Conditional Formula (1-1) below issatisfied:−0.5<(L11f−L12r)/(L11f+L12r)<−0.12  (1-1) wherein L1 if is the paraxialradius of curvature of the surface of the 1-1 negative lens toward theobject side, and L12r is the paraxial radius of curvature of the surfaceof the 1-2 positive lens toward the image side.
 14. A zoom lens asdefined in claim 1, in which Conditional Formula (3-1) below issatisfied:0.7<f2/f21<1.1  (3-1) wherein f2 is the paraxial focal length of thesecond lens group with respect to the d line, and f21 is the paraxialfocal length of the 2-1 negative lens with respect to the d line.
 15. Azoom lens as defined in claim 7, in which Conditional Formula (4-1)below is satisfied:0.9<f3/f34<1.5  (4-1) wherein f3 is the paraxial focal length of thethird lens group with respect to the d line, and f34 is the paraxialfocal length of the 3-4 positive lens with respect to the d line.
 16. Azoom lens as defined in claim 8, in which Conditional Formula (5-1)below is satisfied:0.3<f3/f31<0.7  (5-1) wherein f3 is the paraxial focal length of thethird lens group with respect to the d line, and f31 is the paraxialfocal length of the 3-1 positive lens with respect to the d line.
 17. Azoom lens as defined in claim 1, wherein: the fifth lens group consistsof a single lens; and Conditional Formula (6-1) below is satisfied:16<νd5<38  (6-1) wherein νd5 is the Abbe's number of the single lenswith respect to the d line.
 18. A zoom lens as defined in claim 11, inwhich Conditional Formula (7-1) below is satisfied:25<νd31<35  (7-1) wherein νd31 is the Abbe's number of the 3-1 positivelens with respect to the d line.
 19. An imaging apparatus comprising:the zoom lens as defined in claim 1; and an imaging element thatreceives images of subjects formed by the zoom lens.